What is pyrolysis?
Pyrolysis is the thermal treatment of a feedstock in an oxygen-limited environment. Treating the feedstock in this way avoids combustion of the raw input material and produces syngas and char.
Syngas is made up of combustible gases and can be combusted in a controlled way for renewable energy production, whilst char is a valuable product in its own right.
If the feedstock material is biomass, the resultant char is known as biochar. This carbon-rich product is even more valuable than char from inorganic sources, and can be used to sequester carbon in soils for hundreds of years.
A self-sustaining process
The pyrolysis process begins with organic feedstock entering the feeder. This feedstock has been dried to below 20% moisture content.
The feedstock enters into the reactor, where it is heated to above 600 degrees. Feedstock in the chamber is thermally decomposed into syngas and biochar.
Crucially, this syngas is then combusted in a separate chamber to provide the heat required for the process. Because of this, no external heat source is required to power the process once it has been started.
The pyrolysis conditions can be altered to change the outputs of the process. This can be used to achieve project specific goals, for example maximum carbon sequestration in the biochar, or maximum syngas yield.
The parameters that can be altered include:
- Residence time
- Heating rate
- Amount of oxygen present
Clean energy production
One of the advantages of pyrolysis compared to other waste to energy technologies is the cleaner energy production.
Cleaning the syngas before combusting allows for cleaner combustion compared to combustion of solid fuel.
The sophisticated filtration system used in pyrolysis means less pollutants and particulate matter are emitted. As well as this, the absence of oxygen reduces the number of dioxins that can be formed.
In processes like incineration, heavy metals from the feedstock can leach from the ash created into landfill or soil. The stable nature of biochar reduces this leaching, and even offers opportunity for heavy metal recovery. PAHs in the feedstock are removed during the pyrolysis process.
How does pyrolysis compare with other renewables?
Pyrolysis is the only sustainable energy source that is carbon negative, not just carbon neutral.
While solar, wind and most biomass energy is used to generate electricity, pyrolysis is at its best supplying a heat or cold energy source locally. If that’s what is needed, there are considerable advantages over other methods.
Pyrolysis has been in use since ancient times, and there is evidence that biochar has been used as a soil additive in South America for thousands of years.
The availability of specialist equipment has seen a sharp increase in capacity with 250 working plants worldwide. And the recent recognition of the technology by regulatory bodies as a certified carbon removal method means we are at the beginning of a huge increase in interest and deployment.
Pyrolysis using biomass in Europe is currently removing 100,000 tCO2e from the atmosphere annually, compared to only 4,000 tCO2e by direct air capture (DACCS), making it by far the most effective carbon
removal technology available. As this becomes more widely understood we can expect a major proliferation of the technology in the coming years.
What is Biochar?
Volatile solids are gasified, and the biomass is transformed into a carbon rich product.
The resulting biochar has up to 90% fixed carbon which makes it a valuable carbon sink.
Biochar's many properties make it an excellent soil additive, but it can also be used for a variety of other applications
Biochar is a recalcitrant which means it can endure in soils for hundreds of years
Find out more
Our Green Energy Hubs produce large amounts of excess heat which can be delivered as a fully sustainable, carbon negative energy source for your business.
Pyrolysis is the only practical and available carbon removal technology available today, and is a critical tool for the world's journey to Net Zero.
Biochar is a long-term store of carbon, and an effective soil additive improving plant yields and health. We are committed to producing it on a large scale to make a real difference in the fight against climate change.